To avoid possibility of cross-contamination we have always had mesh across the
end of the pipe from the second settling tank to the pump and of a finer mesh
size than that of the flot mesh, so anything that does get sucked up should
equally wash through the flot sieve - and yes we have used re-cycling systems
even up here in the extremely wet north. It does occasionally need sludge
scraping off; frequency depends highly upon nature of sediment obviously (silty
clays are horrid). We do rinse flots in fresh water but that could always then
go into the system.
Jacqui
Quoting Mark Nesbitt <[log in to unmask]>:
> Hi Lisa
>
> I used a reycling system in Bahrain - it worked fine. We used a
> floation machine flowing into *two* large settling tanks, with the
> pump drawing water from the second tank. Most of the heavy silt
> settles in the first tank. A spare water tank held water for cleaning
> out the floation machine after every 200 litres of soil.
>
> A water tanker came every 5 days, when I took the opportunity to
> clean the whole system, but we could have doe this less often.
>
> I think cross-contamination between samples (from the recycled
> water) is unlikely, as (a) the recycled water is drawn from below the
> surface, whereas charred remains will (mostly) be floating at the
> surface and (b) I doubt that wet charred remains would survive
> passage through a pump. But it would be easy to check this during
> operation. But for a multi-period site it would be best to batch
> samples, with complete cleaning of the machine between samples
> of different periods.
>
> Mark
>
> On 30 May 2006, at 12:34, Lisa Gray wrote:
>
> > Dear all,
> >
> > I'm hoping to help set up a flotation system in Kent this summer. My
> > client has a water meter and we're facing drought orders (hosepipe
> > bans and threats of stand pipes)in the South East of England (bizzare
> > but true) so water use will have to be carefully managed. I've read
> > about water recycling flotation systems and I'm wondering what the
> > experiences are of people who've used them. I'm also hoping those of
> > you used to working in dry environments or situations where you can't
> > use mains water can give me some design advice or point out some
> > useful publications
> >
> > all the best,
> >
> > Lisa
> >
> > Lisa Gray MSc
> > Freelance Archaeobotanist
> > 89 St. John's Rd,
> > Faversham,
> > Kent,
> > ME13 8EN
> > 01795 590603/ 07812028697
>
>
>
> *********************************
> Dr Mark Nesbitt
> Centre for Economic Botany
> Royal Botanic Gardens
> Kew
> Richmond, Surrey
> TW9 3AE
>
> Tel (direct): +44 (0)20 8332 5719
> Fax: +44 (0)20 8332 5768
> Visit www.plantcultures.org.uk
>
>
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